1. Field of the Invention
The present invention relates to a method an apparatus which checks interference among parts operable with numerical control information in a numerical control machine tool.
2. Description of the Prior Art
In the numerical control (referred to as "NC" hereinafter) machine tool which is controlled by an NC apparatus operating by interpreting NC information, because tools, turrets, loaders and measurement devices are being operated simultaneously, it is highly important to check and avoid interference among moving parts or between a moving part and a static part. There has been proposed an apparatus for the tools where the operating range is limited within a two dimensional space such as a lathe, which apparatus checks interference among parts by defining in a two dimensional space the shapes of the tool, the turrets, the chuck, the work or the like and then checking the interference among thus defined shape data in two-dimensional space. There has also been proposed an apparatus for a system where the operating range of the tool extends into the three-dimensional space such as a machining center, which apparatus defines the shapes of the work or fixing jig on an X-Y plane and at the same time defines their thicknesses in a Z-direction, and checks the interference among thus defined shape data and Z-coordinate of the cutter tip of the tool virtually in the two-dimensional space.
However, since the number of movable parts in the machining increases and their movements become complex, above mentioned apparatus are not quite satisfactory because of the following reasons. In a lathe, even though the movement of a tool is restricted in the two-dimensional space, it is impossible to check the interference which might occur between a loader and the tool or with a turret only in terms of the two-dimensional space. Moreover, in the machining center, as shown in FIG. 1, the shape of the work is not necessarily uniform in the Z-direction. When the shape of the work is complicated, precise checking of the interference is difficult.
In order to solve the above problems, there has been proposed an apparatus for strict interference checking in which the shape data of the three-dimensional coordinate system are projected on the three planes, each of which is orthogonal to the other and each of which includes two of the coordinate axes of the three-dimensional coordinate system, in which a determination is made as to whether or not the projected data in each of the planes overlap, and in which it is then determined that the interference has occurred if the projected data are overlapping in all the planes.
The above mentioned interference checking apparatus in an NC machine tool has to strictly define the shapes of moving and static parts in order to deal with complicated shapes of works or with complex movements of moving parts, taking a longer time in processing compared to the apparatus which only define simple shapes.